1. Field of the Invention
The present invention relates to liquid crystal displays (LCDs). More particularly, the present invention relates to a backlight unit for a liquid crystal display module (LCM) incorporating a thermoelectric device.
2. Discussion of the Related Art
In general, notebook personal computers (NTPCs) and laptop computers are dimensionally compact, allowing users to access information stored thereon while on the move. NTPCs typically incorporate liquid crystal display (LCD) devices having LCD modules (LCMs). A typical LCM includes a liquid crystal (LC) panel and a driving circuit unit. The LC panel generally consists of two glass substrates having pixels arranged in matrix pattern and a plurality of switching elements for controlling signals supplied to the pixels. The driving circuit unit drives the LC panel by transmitting the controlling signals to the switching elements.
By itself, an LC panel does not emit light. Rather, LC panels selectively transmit light emitted from an external light source so as to display images. Such external light sources are usually provided as backlight units having a lamp.
FIG. 1 illustrates a cross-sectional view of a related art liquid crystal display module (LCM).
The related art LCM includes a main support 14, a liquid crystal (LC) panel 2 disposed within the main support 14, a top case 10 completely covering the main support 14 and partially covering an edge of the LC panel 2, a backlight unit disposed under the LC panel 2, and a bottom case 12 disposed under, and accommodating, the backlight unit. The main support 14 and the top case 10 are secured to each other by a screw (not shown).
The LC panel 2 typically includes two substrates separated by a liquid crystal layer (not shown). Upper and lower polarizers 42 and 40 are arranged on outwardly opposing surfaces of the two substrates, liquid crystal pixels are arranged in a matrix pattern between the two substrates, and thin film transistors (TFTs) are also provided in a matrix pattern to drive the liquid crystal pixels.
The top case 10 can be die-cast to have an L-shaped cross section and to cover a side of the main support 14 as well as the edge of the LC panel 2. The main support 14 is typically formed of a thermally conductive metal material such as aluminum (Al).
The backlight unit generally includes a lamp 20 that emits light, a lamp housing 16 having an opening and surrounding the lamp 20, a light guide plate 24, a reflector 26, and optical sheets 32, 34, and 36. The reflector 26 is disposed over the bottom case 12, the light guide plate 24 and optical sheets (i.e., diffusing sheet 32, a first prism sheet 34, and a second prism sheet 36) are sequentially disposed over the reflector 26, and the LC panel 2 is disposed over the optical sheets 32, 34, and 36 and is also surrounded by the main support 14. Although not shown, the upper side of light guide plate 24 is flat while the lower side of light guide plate 24 is tapered, enabling the light guide plate 24 to convert the light emitted by the lamp 20 from linear light into planar light. The lamp 20 and the lamp housing 16 are disposed at a side of the light guide plate 24 such that the opening of the lamp housing 16 is arranged adjacent to the side of the light guide plate 24. Accordingly, the backlight arrangement shown in FIG. 1 illustrates what is known as a side-type backlight arrangement.
The lamp 20 is typically provided as a cold cathode fluorescent lamp (CCFL) and includes electrodes formed at opposing ends thereof. Light emitted by the lamp 20 is reflected by the interior of the lamp housing 16, or is otherwise transmitted directly, through the opening of the lamp housing 16 to the light guide plate 24. The reflector 26 reflects light transmitted through the lower side of the light guide plate 24 back into the light guide plate 24 and through the upper side of the light guide plate 24 to reduce light loss of the backlight unit and to uniformly transmit toward the LC panel 2. Light transmitted through the upper side of the light guide plate 24 is evenly diffused by the diffusing sheet 32. The diffused light is then transmitted through the first and second prism sheets 34 and 36 and condensed within predetermined angles with respect to a normal line to the LC panel 2.
Constructed as described above, the related art LCM is commonly used within display devices of monitors, televisions, and display devices that are driven by high voltage and high currents. During operation, temperatures of electrodes at the opposing sides of the lamp 20 can reach about 200° C. Such high temperatures deleteriously damage components within the LCM near the electrodes (e.g., the light guide plate 24), thereby reducing the lifetime and reliability of the LCM.